This invention relates to a blood reservoir for use in an extracorporeal blood circuit. In particular, this invention relates to a means for preventing self-adhesion of a one-way air outlet valve in the blood reservoir.
In cardiopulmonary bypass operations, a patient""s circulatory system is linked to a heart-lung machine to permit the extracorporeal circulation of blood. In these surgical procedures, a bypass circuit is created where venous blood bypasses the heart and is reintroduced into an artery. Also, cardiotomy blood is scavenged from the surgical site, combined with the venous blood, and reintroduced into the patient. The extracorporeal bypass circuit performs numerous functions, including removing emboli and particulate matter entrained in the blood, regulating the carbon dioxide and oxygen content of the blood, and regulating the blood temperature.
In the past, venous blood was filtered and collected in a venous reservoir and the cardiotomy blood was filtered and collected in a cardiotomy reservoir. Work in this art area has included efforts to simplify and improve these systems, as, for example, providing combined venous and cardiotomy reservoir systems. Other work has been directed to simplifying and improving the blood storage, filtration, and defoaming systems for both venous and cardiotomy blood.
In some systems, a sealed venous reservoir is used. This allows a vacuum to be pulled in the reservoir for the purpose of assisting the removal of blood from the patient. However, using such sealed systems creates a potential problem. During the surgical procedure, it is possible to develop either over-or under-pressure situations within the sealed reservoir. Either situation can lead to undesirable consequences for the patient. Therefore, it is known to use safety valves which can regulate the pressure within the sealed reservoir so that it does not exceed acceptable positive and negative pressure limits.
Safety valves include unidirectional valves such as umbrella valves and duck-bill valves. A unidirectional valve permits the escape of air when there is a positive or negative air pressure within the reservoir. Umbrella valves typically are used to vent negative pressure in a reservoir. Duck-bill valves typically are used to vent positive pressure. This valve includes two tips or flaps and an integral base defining a generally cylindrical opening. The tips or flaps butt against each other preventing the passage of air in or out of the reservoir, responding to positive pressure within the reservoir by spreading apart. Duck-bill valves in current use typically are comprised of silicone materials which are engineered to respond to certain pressures, thus allowing fluid to flow through the valve at desired pressures.
We have discovered that the tips or flaps of duck-bill valves used as air outlet valves in blood reservoirs can adhere together after long periods of time or after exposure to adverse environmental conditions. Typically such valves comprise silicone. This self-adhesion is an extremely undesirable situation, as a non-functioning valve can produce a build-up of pressure in a venous reservoir, resulting in reverse blood flow. Thus, a need exists to prevent the self-adhesion of duck-bill valve tips when the duck bill valve is used as a safety valve in blood reservoirs.
We have invented a device, termed an xe2x80x9cobturatorxe2x80x9d, which prevents the tips or flaps of a duck-bill valve from self-adhering during storage or during sterilization procedures. The obturator holds the tips apart until the end-user is ready to use the valve. The duckbill valve is used as an air outlet valve in blood reservoirs.
In one aspect, this invention is a method for preventing self-adhesion of the tips of a duck-bill valve during sterilization by providing an obturator having a plunger element; and inserting the plunger element between the tips of the duck-bill valve prior to sterilization.
The plunger element may be comprised of polymeric materials. Preferably, the plunger element is joined to a cap for ease of insertion and removal. More preferably, the plunger element and the cap are formed or molded from a single piece of plastic.
In a second aspect, this invention is a sealed blood reservoir comprising a top, a bottom, and a continuous sidewall, the top and bottom connected to the sidewall to form a sealed housing; the sealed housing defining an interior chamber; the housing having a blood inlet and a blood outlet in flow communication with the interior chamber; a duck-bill valve having two tips and an integral body in communication with the interior chamber; and an obturator comprising a plunger element positioned between and separating the tips of the duck-bill valve.
In a third aspect, this invention is a method of preventing pressurization of a sealed blood reservoir by providing a sealed blood reservoir as described above, providing a duck-bill valve having two tips and an integral body in communication with the interior chamber of the reservoir; and inserting a plunger element between the tips of the duck-bill valve, wherein the plunger element prevents the tips of the duck-bill valve from self-adhering.